Organic compound, and organic light emitting diode and organic light emitting display device including the same

ABSTRACT

The present disclosure provides an organic compound of following formula and an organic light emitting diode and an OLED device including the organic compound.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of Korean Patent ApplicationNo. 10-2019-0088995 filed in the Republic of Korea on Jul. 23, 2019,which is hereby incorporated by reference in its entirety.

BACKGROUND Field of Technology

The present disclosure relates to an organic compound, and moreparticularly, to an organic compound having high triplet energy andbeing used for an n-type host, and an organic light emitting diode andan organic light emitting display (OLED) device including the organiccompound.

Discussion of the Related Art

Recently, requirement for flat panel display devices having smalloccupied area is increased. Among the flat panel display devices, atechnology of an OLED device, which includes an organic light emittingdiode and may be called to as an organic electroluminescent device, israpidly developed.

The organic light emitting diode emits light by injecting electrons froma cathode as an electron injection electrode and holes from an anode asa hole injection electrode into an organic emitting layer, combining theelectrons with the holes, generating an exciton, and transforming theexciton from an excited state to a ground state. A flexible transparentsubstrate, for example, a plastic substrate, can be used as a basesubstrate where elements are formed. In addition, the organic lightemitting diode can be operated at a voltage (e.g., 10\T or below) lowerthan a voltage required to operate other display devices and has lowpower consumption. Moreover, the light from the organic light emittingdiode has excellent color purity.

An emitting material layer of the organic emitting layer includes a hostand a dopant. For example, an organic compound such as CBP may widely beused as the host of the emitting material layer.

However, in the related art organic light emitting diode, expectedlifespan and emitting efficiency are not provided. Namely, there is alimitation in the lifespan and the emitting efficiency of the organiclight emitting diode and the OLED device.

SUMMARY

The present disclosure is directed to an organic compound, an organiclight emitting diode and an OLED device that substantially obviate oneor more of the problems associated with the limitations anddisadvantages of the related conventional art.

Additional features and advantages of the present disclosure are setforth in the description which follows, and will be apparent from thedescription, or evident by practice of the present disclosure. Theobjectives and other advantages of the present disclosure are realizedand attained by the features described herein as well as in the appendeddrawings.

To achieve these and other advantages in accordance with the purpose ofthe embodiments of the present disclosure, as described herein, anaspect of the present disclosure comprises an organic compound of:

wherein each of X, Y, and Z is independently selected from hydrogen anda C1 to C20 alkyl group, and at least one of X, Y, and Z is selectedfrom the C1 to C20 alkyl group, and wherein each of D1 and D2 isindependently selected from a C10 to C60 heteroaryl group.

In another aspect, an organic light emitting diode comprises a firstelectrode; a second electrode facing the first electrode; and a firstemitting material layer between the first and second electrodes andincluding an organic compound of:

wherein each of X, Y, and Z is independently selected from hydrogen anda C1 to C20 alkyl group, and at least one of X, Y, and Z is selectedfrom the C1 to C20 alkyl group, and wherein each of D1 and D2 isindependently selected from a C10 to C60 heteroaryl group.

In another aspect, an organic light emitting display device comprises asubstrate; an organic light emitting diode disposed on or over thesubstrate, the organic light emitting diode including: a firstelectrode; a second electrode facing the first electrode; and a firstemitting material layer between the first and second electrodes; and athin film transistor positioned between the substrate and the organiclight emitting diode and connected to the organic light emitting diode,wherein the first emitting material layer includes an organic compoundof:

wherein each of X, Y, and Z is independently selected from hydrogen anda C1 to C20 alkyl group, and at least one of X, Y, and Z is selectedfrom the C1 to C20 alkyl group, and wherein each of D1 and D2 isindependently selected from a C10 to C60 heteroaryl group.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to further explain the present disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the present disclosure and are incorporated in andconstitute a part of this specification, illustrate embodiments of thepresent disclosure and together with the description serve to explainprinciples of the present disclosure.

FIG. 1 is a schematic circuit diagram of an OLED device of the presentdisclosure.

FIG. 2 is a schematic cross-sectional view of an OLED device of thepresent disclosure.

FIG. 3 is a schematic cross-sectional view of an organic light emittingdiode of the present disclosure.

FIGS. 4A and 4B are schematic view illustrating emission in an organiclight emitting diode using a p-type host and an organic light emittingdiode of the present disclosure, respectively.

FIG. 5 is a view illustrating an emission mechanism of a delayedfluorescent compound.

FIG. 6 is a view illustrating an emission mechanism of an organic lightemitting diode of the present disclosure.

FIG. 7 is a schematic cross-sectional view of an organic light emittingdiode of the present disclosure.

FIG. 8 is a schematic cross-sectional view of an organic light emittingdiode of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to some of the examples andpreferred embodiments, which are illustrated in the accompanyingdrawings.

FIG. 1 is a schematic circuit diagram of an OLED device of the presentdisclosure.

As shown in FIG. 1 , an OLED device includes a gate line GL, a data lineDL, a power line PL, a switching thin film transistor TFT Ts, a drivingTFT Td, a storage capacitor Cst, and an organic light emitting diode D.The gate line GL and the data line DL cross each other to define a pixelregion SP.

The switching TFT Ts is connected to the gate line GL and the data lineDL, and the driving TFT Td and the storage capacitor Cst are connectedto the switching TFT Ts and the power line PL. The organic lightemitting diode D is connected to the driving TFT Td.

In the OLED device, when the switching TFT Ts is turned on by a gatesignal applied through the gate line GL, a data signal from the dataline DL is applied to the gate electrode of the driving TFT Td and anelectrode of the storage capacitor Cst.

When the driving TFT Td is turned on by the data signal, an electriccurrent is supplied to the organic light emitting diode D from the powerline PL. As a result, the organic light emitting diode D emits light. Inthis case, when the driving TFT Td is turned on, a level of an electriccurrent applied from the power line PL to the organic light emittingdiode D is determined such that the organic light emitting diode D canproduce a gray scale.

The storage capacitor Cst serves to maintain the voltage of the gateelectrode of the driving TFT Td when the switching TFT Ts is turned off.Accordingly, even if the switching TFT Ts is turned off, a level of anelectric current applied from the power line PL to the organic lightemitting diode D is maintained to next frame.

As a result, the OLED device displays a desired image.

FIG. 2 is a schematic cross-sectional view of an OLED device of thepresent disclosure.

As shown in FIG. 2 , the OLED device 100 includes a substrate 110, a TFTTr and an organic light emitting diode D connected to the TFT Tr.

The substrate 110 may be a glass substrate or a plastic substrate. Forexample, the substrate 110 may be a polyimide substrate.

A buffer layer 120 is formed on the substrate, and the TFT Tr is formedon the buffer layer 120. The buffer layer 120 may be omitted.

A semiconductor layer 122 is formed on the buffer layer 120. Thesemiconductor layer 122 may include an oxide semiconductor material orpolycrystalline silicon.

When the semiconductor layer 122 includes the oxide semiconductormaterial, a light-shielding pattern (not shown) may be formed under thesemiconductor layer 122. The light to the semiconductor layer 122 isshielded or blocked by the light-shielding pattern such that thermaldegradation of the semiconductor layer 122 can be prevented. On theother hand, when the semiconductor layer 122 includes polycrystallinesilicon, impurities may be doped into both sides of the semiconductorlayer 122.

A gate insulating layer 124 is formed on the semiconductor layer 122.The gate insulating layer 124 may be formed of an inorganic insulatingmaterial such as silicon oxide or silicon nitride.

A gate electrode 130, which is formed of a conductive material, e.g.,metal, is formed on the gate insulating layer 124 to correspond to acenter of the semiconductor layer 122.

In FIG. 2 , the gate insulating layer 124 is formed on an entire surfaceof the substrate 110. Alternatively, the gate insulating layer 124 maybe patterned to have the same shape as the gate electrode 130.

An interlayer insulating layer 132, which is formed of an insulatingmaterial, is formed on the gate electrode 130. The interlayer insulatinglayer 132 may be formed of an inorganic insulating material, e.g.,silicon oxide or silicon nitride, or an organic insulating material,e.g., benzocyclobutene or photo-acryl.

The interlayer insulating layer 132 includes first and second contactholes 134 and 136 exposing both sides of the semiconductor layer 122.The first and second contact holes 134 and 136 are positioned at bothsides of the gate electrode 130 to be spaced apart from the gateelectrode 130.

The first and second contact holes 134 and 136 are formed through thegate insulating layer 124. Alternatively, when the gate insulating layer124 is patterned to have the same shape as the gate electrode 130, thefirst and second contact holes 134 and 136 is formed only through theinterlayer insulating layer 132.

A source electrode 140 and a drain electrode 142, which are formed of aconductive material, e.g., metal, are formed on the interlayerinsulating layer 132.

The source electrode 140 and the drain electrode 142 are spaced apartfrom each other with respect to the gate electrode 130 and respectivelycontact both sides of the semiconductor layer 122 through the first andsecond contact holes 134 and 136.

The semiconductor layer 122, the gate electrode 130, the sourceelectrode 140 and the drain electrode 142 constitute the TFT Tr. The TFTTr serves as a driving element.

In the TFT Tr, the gate electrode 130, the source electrode 140, and thedrain electrode 142 are positioned over the semiconductor layer 122.Namely, the TFT Tr has a coplanar structure.

Alternatively, in the TFT Tr, the gate electrode may be positioned underthe semiconductor layer, and the source and drain electrodes may bepositioned over the semiconductor layer such that the TFT Tr may have aninverted staggered structure. In this instance, the semiconductor layermay include amorphous silicon.

Although not shown, the gate line and the data line cross each other todefine the pixel region, and the switching TFT is formed to be connectedto the gate and data lines. The switching TFT is connected to the TFT Tras the driving element.

In addition, the power line, which may be formed to be parallel to andspaced apart from one of the gate and data lines, and the storagecapacitor for maintaining the voltage of the gate electrode of the TFTTr in one frame may be further formed.

A passivation layer 150, which includes a drain contact hole 152exposing the drain electrode 142 of the TFT Tr, is formed to cover theTFT Tr.

A first electrode 160, which is connected to the drain electrode 142 ofthe TFT Tr through the drain contact hole 152, is separately formed ineach pixel region. The first electrode 160 may be an anode and may beformed of a conductive material having a relatively high work function.For example, the first electrode 160 may be formed of a transparentconductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide(IZO).

When the OLED device 100 is operated in a top-emission type, areflection electrode or a reflection layer may be formed under the firstelectrode 160. For example, the reflection electrode or the reflectionlayer may be formed of aluminum-palladium-copper (APC) alloy.

A bank layer 166 is formed on the passivation layer 150 to cover an edgeof the first electrode 160. Namely, the bank layer 166 is positioned ata boundary of the pixel region and exposes a center of the firstelectrode 160 in the pixel region.

An organic emitting layer 162 is formed on the first electrode 160. Theorganic emitting layer 162 may have a single-layered structure of anemitting material layer including an emitting material. To increase anemitting efficiency of the OLED device, the organic emitting layer 162may have a multi-layered structure.

A second electrode 164 is formed over the substrate 110 where theorganic emitting layer 162 is formed. The second electrode 164 covers anentire surface of the display area and may be formed of a conductivematerial having a relatively low work function to serve as a cathode.For example, the second electrode 164 may be formed of aluminum (Al),magnesium (Mg) or Al—Mg alloy.

The first electrode 160, the organic emitting layer 162 and the secondelectrode 164 constitute the organic light emitting diode D.

An encapsulation film 170 is formed on the second electrode 164 toprevent penetration of moisture into the organic light emitting diode D.The encapsulation film 170 includes a first inorganic insulating layer172, an organic insulating layer 174 and a second inorganic insulatinglayer 176 sequentially stacked, but it is not limited thereto.

A polarization plate (not shown) for reducing an ambient lightreflection may be disposed over the top-emission type organic lightemitting diode D. For example, the polarization plate may be a circularpolarization plate.

In addition, a cover window (not shown) may be attached to theencapsulation film 170 or the polarization plate. In this instance, thesubstrate 110 and the cover window have a flexible property such that aflexible OLED device may be provided.

FIG. 3 is a schematic cross-sectional view of an organic light emittingdiode of the present disclosure.

As shown in FIG. 3 , the organic light emitting diode D includes thefirst and second electrodes 160 and 164, which face each other, and theorganic emitting layer 162 therebetween. The organic emitting layer 162includes an emitting material layer (EML) 240 between the first andsecond electrodes 160 and 164, a hole transporting layer (HTL) 220between the first electrode 160 and the EML 240 and an electrontransporting layer (ETL) 260 between the second electrode 164 and theEML 240.

In addition, the organic emitting layer 162 may further include a holeinjection layer (HIL) 210 between the first electrode 160 and the HTL220 and an electron injection layer (EIL) 270 between the secondelectrode 164 and the ETL 260.

Moreover, the organic emitting layer 162 may further include an electronblocking layer (EBL) 230 between the HTL 220 and the EML 240 and a holeblocking layer (HBL) 250 between the EML 240 and the ETL 260.

The organic emitting layer 162, preferably the EML 240 includes anorganic compound of Formula 1 as a host and further includes a dopant.

In Formula 1, each of X, Y, and Z is independently selected fromhydrogen and a C1 to C20 alkyl group, and at least one of X, Y, and Z isselected from a C1 to C20 alkyl group. It is preferable that one or twoof X, Y and Z may be a C1 to C10 alkyl group.

For example, at least one of X, Y and Z may be selected from the groupconsisting of methyl, ethyl, propyl (iso-propyl) and butyl (t-butyl). Itis preferable that at least one of X, Y and Z may be methyl.

In addition, each of D1 and D2 is independently selected from a C10 toC60 heteroaryl group. D1 and D2 are same or different. The heteroarylincludes substituted or non-substituted heteroaryl. For example, each ofD1 and D2 may be selected from the group consisting of substituted ornon-substituted carbazolyl, substituted or non-substituteddibenzofuranyl and substituted or non-substituted dibenzothiophenyl. Inthis instance, the substituent may be carbazole group or cyano group.

For example, D1 and D2 may be combined the phenyl moiety at ameta-position and may be selected from Formula 2.

Namely, in the organic compound of the present disclosure, an electronacceptor moiety, which is a substituted or non-substituted pyridylgroup, and an electron donor moiety, which is a substituted ornon-substituted C10 to C60 heteroaryl group, are combined (connected) toa substituted or non-substituted phenylene linker. In other words, theorganic compound of the present disclosure includes two electron donormoieties and thus has n-type properties. In addition, since the electronacceptor moiety and/or the linker is substituted by a C1 to C10 alkylgroup, the decrease of the triplet energy of the organic compound by then-type property is prevented. Moreover, the organic compound of thepresent disclosure has a bipolar characteristic, thereby improving thecharge balance in the EML. As a result, the emitting efficiency of theorganic light emitting diode and the OLED device is improved.

Accordingly, the organic compound of the present disclosure has then-type property and high triplet energy.

The organic compound of the present disclosure may be used as an n-typehost. As described above, the organic compound of the present disclosurehas high triplet energy, the organic light emitting diode and the OLEDdevice including the organic compound as the host in the EML haveadvantages in the emitting efficiency and the lifespan.

In the EML 240, the quenching problem of the exciton by an interactionbetween the triplet exciton of the dopant and the hole-polaron may begenerated. To prevent the quenching problem, n-type host is required.However, when the n-type property of the host is increased, the tripletenergy of the host is decreased such that the triplet exciton of thedopant is transited into the triplet energy level of the host. As aresult, the emitting efficiency is decreased.

However, in the organic compound of the present disclosure since theelectron acceptor moiety, which is a substituted or non-substitutedpyridyl group, and the electron donor moiety, which is a substituted ornon-substituted C10 to C60 heteroaryl group, are combined (connected) toa substituted or non-substituted phenylene linker and the electronacceptor moiety and/or the linker is substituted by a C1 to C10 alkylgroup, the organic compound has high triplet energy.

Accordingly, in the organic light emitting diode D of the presentdisclosure, the quenching problem of the exciton by an interactionbetween the triplet exciton of the dopant and the hole-polaron and theenergy transiting problem from the dopant to the host by low tripletenergy of the host are prevented or minimized.

In addition, when the organic compound of the present disclosure is usedas the n-type host, the emitting zone, i.e., a recombination zone,resulting from the combination between the hole and the electron isgenerated at a region near an interface between the EML and the EBL suchthat the lifespan of the organic light emitting diode is improved.

Namely, referring to FIG. 4A, which is a view illustrating emission inan organic light emitting diode using a p-type host, the mobility of thehole becomes relatively fast due to the p-type host in the EML such thatthe emitting zone (recombination zone) is generated to be near aninterface between the EML and the HBL.

On the other hand, referring to FIG. 4B, which is a view illustratingemission in an organic light emitting diode of the present disclosure,the mobility of the electron becomes relatively fast due to the n-typehost, i.e., the organic compound of the present disclosure, in the EMLsuch that the emitting zone (recombination zone) is generated to be nearan interface between the EML and the EBL.

A position of the emitting zone is shifted by the property differencebetween the p-type host and the n-type host such that the lifespan ofthe organic light emitting diode (D) is also changed.

In all cases of the light emitting diodes using the p-type host and then-type host, the emitting zone is generated to be shifted one side ofthe EML. However, when the emitting zone is generated to be closer tothe first electrode, for example, in a region near an interface betweenone of the EBL and the HTL and the EML, the emitting efficiency and thelifespan of the organic light emitting diode are improved.

The dopant used to the EML 240 with the organic compound of the presentdisclosure as the host may be at least one of a fluorescent compound(fluorescent dopant), a phosphorescent compound (phosphorescent dopant)and a delayed fluorescent compound (delayed fluorescent dopant). Thedopant may have a weight ratio, i.e., wt %, of about 1 to 50 withrespect to the host.

For example, referring to FIG. 5 , which is a view illustrating anemission mechanism of a delayed fluorescent compound, in the delayedfluorescent compound, the singlet exciton and the triplet exciton areengaged in the emission such that the quantum efficiency is improved.

Namely, in the delayed florescent compound, when the triplet exciton isactivated by a field or heat, and the triplet exciton and the singletexciton are transferred into an intermediated state and transited into aground state to emit light. In other words, the singlet state and thetriplet state are engaged in the emission such that the emittingefficiency is improved.

When the EML 240 includes the delayed fluorescent dopant (delayedfluorescent compound) with the organic compound of the presentdisclosure as the host, a difference between the HOMO of the host“HOMO_(Host)” and the HOMO of the delayed fluorescent dopant“HOMO_(Dopant)” or a difference between the LUMO of the host“LUMO_(Host)” and the LUMO of the delayed fluorescent dopant“LUMO_(Dopant)” is less than about 0.5 eV. In this instance, the chargetransfer efficiency from the host to the dopant may be improved.

The triplet energy of the delayed fluorescent dopant is smaller than thetriplet energy of the host, and a difference between the singlet energyof the delayed fluorescent dopant and the triplet energy of the delayedfluorescent dopant is less than 0.3 eV. (ΔE_(ST)≥0.3 eV.) As thedifference “ΔE_(ST)” is smaller, the emitting efficiency is higher. Inaddition, even if the difference “ΔE_(ST)” between the singlet energy ofthe delayed fluorescent dopant and the triplet energy of the delayedfluorescent dopant is about 0.3 eV, which is relatively large, theexcitons in the singlet state and the excitons in the triplet state canbe transited into the intermediate state.

The EML 240 may include the organic compound of the present disclosureas the host with the delayed fluorescent dopant as a first dopant andthe fluorescent dopant as a second dopant. The summation of the firstdopant and the second dopant may be about 1 to 50 wt % with respect tothe host.

The singlet energy of the first dopant may be smaller than that of thehost and larger than that of the second dopant. The triplet energy ofthe first dopant may be smaller than that of the host and larger thanthat of the second dopant.

Referring to FIG. 6 , which is a view illustrating an emission mechanismof an organic light emitting diode of the present disclosure, thetriplet energy (E_(T1)(TD)) of the delayed fluorescent dopant, i.e., thefirst dopant, is converted into the singlet energy (E_(s1)(TD)) by aneffect of a reverse intersystem crossing (RISC), and the singlet energy(E_(s1)(TD)) of the delayed fluorescent dopant is transferred into thesinglet energy (E_(s1)(FD)) of the fluorescent dopant, i.e., the seconddopant by an effect of Foster resonance energy transfer. As a result,the light is emitted from the fluorescent dopant.

In the organic light emitting diode D, since the EML 240 includes thehost, the first dopant and the second dopant, the emitting efficiencyand the color purity are improved. Namely, since the energy istransferred from the host into the first dopant and both the singletenergy and the triplet energy of the first dopant are transferred intothe second dopant, the emission is generated from the second dopant suchthat the quantum efficiency of the organic light emitting diode D isincreased and the full width at half maximum (FWHM) of the light fromthe organic light emitting diode D is narrowed.

The delayed fluorescent dopant as the first dopant has high quantumefficiency. However, since the light emitted from the delayedfluorescent dopant has wide FWHM, the light from the delayed fluorescentdopant has bad color purity. On the other hand, the fluorescent dopantas the second dopant has narrow FWHM and high color purity. However,since the triplet energy of the fluorescent dopant is not engaged in theemission, the fluorescent dopant has low quantum efficiency.

Since the EML 240 of the organic light emitting diode D in the presentdisclosure includes the host, the first dopant and the second dopant,the organic light emitting diode D has advantages in both the emittingefficiency and the color purity.

In addition, since the organic compound of the present disclosure, whichhas high triplet energy and the n-type property, is used as the host,the emitting efficiency is further improved.

For example, the organic compound of the present disclosure in Formula 1may be one of compounds in Formula 3.

[Synthesis of Organic Compounds]

1. Synthesis of Compound 1-2

(1) Compound C

Under nitrogen condition, the compound A was dissolved in a mixedsolution of tetrahydrofuran and toluene (volume ratio=5:1), and thecompound B (0.9 equivalent) was added. Potassium carbonate (4.0equivalent) was dissolved in the DI water, and Pd(0) (0.04 equivalent)were added. The reaction mixture was refluxed and stirred under thetemperature of 80° C. for 8 hrs, and then the reaction was finished. Theresultant was extracted using an organic solvent, and the organicsolvent was removed. The resultant was columned and reprecipitated suchthat the compound C was obtained.

(2) Compound E

Under nitrogen condition, the compound C was dissolved in toluene, andthe compound D (0.9 equivalent) was added. Sodium t-butoxide (4.0equivalent) was added, and Pd₂(dba)₃ (0.04 equivalent) andtri-tert-butyl phosphine (0.04 equivalent) were added. The mixture wasrefluxed and stirred under the temperature of 80° C. for 24 hrs, andthen the reaction was finished. The resultant was extracted using anorganic solvent, and the organic solvent was removed. The resultant wascolumned and reprecipitated such that the compound E was obtained.

(3) Compound 1-2

Under nitrogen condition, the compound E was dissolved in toluene, andthe compound F (1.2 equivalent) was added. Sodium t-butoxide (4.4equivalent) was added, and Pd₂(dba)₃ (0.05 equivalent) andtri-tert-butyl phosphine (0.05 equivalent) were added. The mixture wasrefluxed and stirred under the temperature of 80° C. for 24 hrs, andthen the reaction was finished. The resultant was extracted using anorganic solvent, and the organic solvent was removed. The resultant wascolumned and reprecipitated such that the compound 1-2 was obtained.

2. Synthesis of Compound 1-6

(1) Compound E′

Under nitrogen condition, the compound C was dissolved in a mixedsolution of tetrahydrofuran and toluene (volume ratio=5:1), and thecompound G (0.9 equivalent) was added. Potassium carbonate (4.0equivalent) was dissolved in the DI water, and Pd(0) (0.04 equivalent)were added. The reaction mixture was refluxed and stirred under thetemperature of 80° C. for 8 hrs, and then the reaction was finished. Theresultant was extracted using an organic solvent, and the organicsolvent was removed. The resultant was columned and reprecipitated suchthat the compound E′ was obtained.

(2) Compound 1-6

Under nitrogen condition, the compound E′ was dissolved in toluene, andthe compound D′ (1.2 equivalent) was added. Sodium t-butoxide (4.4equivalent) was added, and Pd₂(dba)₃ (0.05 equivalent) andtri-tert-butyl phosphine (0.05 equivalent) were added. The mixture wasrefluxed and stirred under the temperature of 80° C. for 24 hrs, andthen the reaction was finished. The resultant was extracted using anorganic solvent, and the organic solvent was removed. The resultant wascolumned and reprecipitated such that the compound 1-6 was obtained.

3. Synthesis of Compound 1-7

(1) Compound E″

Under nitrogen condition, the compound C was dissolved in toluene, andthe compound F (0.9 equivalent) was added. Sodium t-butoxide (4.0equivalent) was added, and Pd₂(dba)₃ (0.04 equivalent) andtri-tert-butyl phosphine (0.04 equivalent) were added. The mixture wasrefluxed and stirred under the temperature of 80° C. for 8 hrs, and thenthe reaction was finished. The resultant was extracted using an organicsolvent, and the organic solvent was removed. The resultant was columnedand reprecipitated such that the compound E″ was obtained.

(2) Compound 1-7

Under nitrogen condition, the compound E″ was dissolved in toluene, andthe compound D′ (1.2 equivalent) was added. Sodium t-butoxide (4.4equivalent) was added, and Pd₂(dba)₃ (0.05 equivalent) andtri-tert-butyl phosphine (0.05 equivalent) were added. The mixture wasrefluxed and stirred under the temperature of 80° C. for 24 hrs, andthen the reaction was finished. The resultant was extracted using anorganic solvent, and the organic solvent was removed. The resultant wascolumned and reprecipitated such that the compound 1-7 was obtained.

4. Synthesis of Compound 2-10

(1) Compound C′

Under nitrogen condition, the compound A′ was dissolved in a mixedsolution of tetrahydrofuran and toluene (volume ratio=5:1), and thecompound B′ (0.8 equivalent) was added. Potassium carbonate (4.0equivalent) was dissolved in the DI water, and Pd(0) (0.04 equivalent)were added. The reaction mixture was refluxed and stirred under thetemperature of 80° C. for 8 hrs, and then the reaction was finished. Theresultant was extracted using an organic solvent, and the organicsolvent was removed. The resultant was columned and reprecipitated suchthat the compound C′ was obtained.

(2) Compound E′″

Under nitrogen condition, the compound C′ was dissolved in toluene, andthe compound D (0.8 equivalent) was added. Potassium phosphate (1.5equivalent), ±-trans-1,2-diaminocyclohexane (0.2 equivalent) and CuI(0.1 equivalent) were added. The mixture was refluxed and stirred underthe temperature of 80° C. for 8 hrs, and then the reaction was finished.The resultant was extracted using an organic solvent, and the organicsolvent was removed. The resultant was columned and reprecipitated suchthat the compound E′″ was obtained.

(2) Compound 2-10

Under nitrogen condition, the compound E/// was dissolved in a mixedsolution of tetrahydrofuran and toluene (volume ratio=5:1), and thecompound G (1.2 equivalent) was added. Potassium carbonate (4.4equivalent) was dissolved in the DI water, and Pd(0) (0.05 equivalent)were added. The reaction mixture was refluxed and stirred under thetemperature of 80° C. for 24 hrs, and then the reaction was finished.The resultant was extracted using an organic solvent, and the organicsolvent was removed. The resultant was columned and reprecipitated suchthat the compound 2-10 was obtained.

The properties, i.e., a HOMO level, a LUMO level and a triplet energylevel (ET), of the compounds 1-1, 1-2, 1-6, 1-7, 2-1, 2-5, 2-8, 2-10,3-1, 3-3, 3-10, 3-13, 4-1, 4-2, 4-3 and 4-4 in Formula 3 and thecompound in Formula 4 are measured and listed in Table 1. (unit: [eV])

TABLE 1 HOMO LUMO Eγ Compound 1-1 −5.41 −1.18 3.16 Compound 1-2 −5.32−1.15 3.09 Compound 1-6 −5.79 −1.50 3.18 Compound 1-7 −5.67 −1.23 3.20Compound 2-1 −5.35 −1.12 3.17 Compound 2-5 −5.20 −1.08 3.09 Compound 2-8−5.26 −1.28 3.01 Compound 2-10 −5.13 −1.21 3.12 Compound 3-1 −5.37 −0.993.11 Compound 3-3 −5.28 −1.05 3.17 Compound 3-10 −5.76 −1.21 3.20Compound 3-13 −5.73 −1.20 3.18 Compound 4-1 −5.16 −0.97 3.09 Compound4-2 −5.16 −1.19 3.08 Compound 4-3 −5.25 −1.03 3.18 Compound 4-4 −5.59−1.23 3.20 Formula 4 −5.61 −126 2.70

As shown in Table 1, in comparison to the compound in Formula 4, whereno alkyl group is substituted to the pyridyl moiety and the phenylenelinker, the organic compound of the present disclosure has highertriplet energy. Accordingly, the organic compound used as the host inthe EML provides high energy efficiency. In addition, since the organiccompound of the present disclosure has the n-type property, the emittingzone is shifted such that the emitting efficiency and the lifespan ofthe organic light emitting diode and the OLED device are improved.

[Organic Light Emitting Diode]

In the vacuum chamber of about 10⁻⁷ Torr, layers are sequentiallydeposited on an ITO substrate.

(a) HIL (50 Å, HATCN), (b) HTL (500 Å, NPB), (c) EBL (100 Å, mCP), (d)EML (300 Å, HOST: Dopant (30 wt %, Formula 5)), (e) ETL (300 Å, TPBI),(f) EIL (10 Å, LiF), and (g) Cathode (1000 Å, Al)

(1) Comparative Example 1 (Ref1)

The compound of Formula 6 is used as the host.

(2) Comparative Example 2 (Ref2)

The compound of Formula 7 is used as the host.

(3) Example 1 (Ex1)

The compound 1-2 of Formula 3 is used as the host.

(4) Example 2 (Ex2)

The compound 1-6 of Formula 3 is used as the host.

(5) Example 3 (Ex3)

The compound 1-7 of Formula 3 is used as the host.

(6) Example 4 (Ex4)

The compound 2-10 of Formula 3 is used as the host.

The properties of the organic light emitting diodes of Ref1, Ref2 andEx1 to Ex4 are measured. The driving voltage, the external quantumefficiency (EQE), the power efficiency (lm/W), the CIE color coordinateof the organic light emitting diodes are listed in Table 2.

TABLE 2 V EQE [%] CIEy Ref 1 4.5 6.4 0.343 Ref 2 4.1 8.8 0.337 EX 1 3.713.2 0.334 Ex 2 3.2 12.2 0.335 Ex 3 3.7 14.5 0.339 Ex 4 3.4 14.1 0.338

As shown in Table 2, in comparison to the organic light emitting diodesof Ref1 and Ref2, the emitting efficiency, e.g., the EQE and the powerefficiency, of the organic light emitting diodes of Ex1 to Ex4 using theorganic compounds of the present disclosure as the host is remarkablyincreased.

FIG. 7 is a schematic cross-sectional view of an organic light emittingdiode of the present disclosure.

As shown in FIG. 7 , an organic light emitting diode D includes thefirst and second electrodes 160 and 164, which face each other, and theorganic emitting layer 162 therebetween. The organic emitting layer 162includes an EML 340, which includes first and second layers 342 and 344and is positioned between the first and second electrodes 160 and 164, aHTL 320 between the first electrode 160 and the EML 340 and an ETL 360between the second electrode 164 and the EML 340.

In addition, the organic emitting layer 162 may further include a HIL310 between the first electrode 160 and the HTL 320 and an EIL 370between the second electrode 164 and the ETL 360.

Moreover, the organic emitting layer 162 may further include an EBL 330between the HTL 320 and the EML 340 and a HBL 350 between the EML 340and the ETL 360.

For example, in the EML 340, the first layer 342 (e.g., a first emittingmaterial layer) may include the organic compound of the presentdisclosure as a first host and a delayed fluorescent dopant as a firstdopant, and the second layer 344 (e.g., a second emitting materiallayer) may include a second host and a fluorescent dopant as a seconddopant. Alternatively, the second layer 344 may include the organiccompound of the present disclosure as a first host and a delayedfluorescent dopant as a first dopant, and the first layer 342 mayinclude a second host and a fluorescent dopant as a second host. Thesecond host may be the organic compound of the present disclosure. Thedelayed fluorescent dopant has a singlet energy being larger than thefluorescent dopant.

The organic light emitting diode, where the first layer 342 includes thedelayed fluorescent dopant and the second layer 344 includes thefluorescent dopant, will be explained.

In the organic light emitting diode D, the singlet energy and thetriplet energy of the delayed fluorescent dopant are transferred intothe fluorescent dopant such that the emission is generated from thefluorescent dopant. Accordingly, the quantum efficiency of the organiclight emitting diode D is increased, and the FWHM of the organic lightemitting diode D is narrowed.

The delayed fluorescent dopant as the first dopant has high quantumefficiency. However, since the light emitted from the delayedfluorescent dopant has wide FWHM, the light from the delayed fluorescentdopant has bad color purity. On the other hand, the fluorescent dopantas the second dopant has narrow FWHM and high color purity. However,since the triplet energy of the fluorescent dopant is not engaged in theemission, the fluorescent dopant has low quantum efficiency.

Since the EML 340 of the organic light emitting diode D in the presentdisclosure includes the first layer 342, which includes the delayedfluorescent dopant, and the second layer 344, which includes thefluorescent dopant, the organic light emitting diode D has advantages inboth the emitting efficiency and the color purity.

The triplet energy of the delayed fluorescent dopant is converted intothe singlet energy of the delayed fluorescent dopant by the RISC effect,and the singlet energy of the delayed fluorescent dopant is transferredinto the singlet energy of the fluorescent dopant. Namely, thedifference between the triplet energy of the delayed fluorescent dopantand the singlet energy of the delayed fluorescent dopant is less than0.3 eV such that the triplet energy of the delayed fluorescent dopant isconverted into the singlet energy of the delayed fluorescent dopant bythe RISC effect.

As a result, the delayed fluorescent dopant has an energy transferfunction, and the first layer 342 including the delayed fluorescentdopant is not engaged in the emission. The emission is generated in thesecond layer 344 including the fluorescent dopant.

The triplet energy of the delayed fluorescent dopant is converted intothe singlet energy of the delayed fluorescent dopant by the RISC effect.In addition, since the singlet energy of the delayed fluorescent dopantis higher than that of the fluorescent dopant, the singlet energy of thedelayed fluorescent dopant is transferred into the singlet energy of thefluorescent dopant. As a result, the fluorescent dopant emits the lightusing the singlet energy and the triplet energy such that the quantumefficiency (emitting efficiency) of the organic light emitting diode Dis improved.

In other words, the organic light emitting diode D and the OLED device100 (of FIG. 2 ) including the organic light emitting diode D hasadvantages in both the emitting efficiency and the color purity.

In each of the first and second layers 342 and 344, the first and secondhosts may have a percentage by weight being larger than the delayedfluorescent dopant and the fluorescent dopant, respectively. Inaddition, the percentage by weight of the delayed fluorescent dopant inthe first layer 342 may be greater than that of the fluorescent dopantin the second layer 344. As a result, the energy transfer from thedelayed fluorescent dopant into the fluorescent dopant is sufficientlygenerated.

The singlet energy of the first host is greater than that of the delayedfluorescent dopant, and the triplet energy of the first host is greaterthan that of the delayed fluorescent dopant. In addition, the singletenergy of the second host is greater than that of the fluorescentdopant.

When not satisfying this condition, a quenching happens at the first andsecond dopants or an energy transfer from the host to the dopant doesnot happen, and thus the quantum efficiency of the organic lightemitting diode D may be reduced.

As mentioned above, since the organic compound of the present disclosurehas high triplet energy, the energy transfer efficiency into the delayedfluorescent compound is increased such that the emitting efficiency ofthe organic light emitting diode D is improved.

In addition, since the organic compound of the present disclosure havingthe n-type property is included in the EML as the host, the quenchingproblem of the exciton by an interaction between the triplet exciton ofthe dopant and the hole-polaron is prevented such that the emittingefficiency of the organic light emitting diode D is further improved.

For example, the second host, which is included in the second layer 344with the fluorescent dopant, may be same as a material of the HBL 350.In this instance, the second layer 344 may have a hole blocking functionwith an emission function. Namely, the second layer 344 may serve as abuffer layer for blocking the hole. When the HBL 350 is omitted, thesecond layer 344 serves as an emitting layer and a hole blocking layer.

When the first layer 342 includes the fluorescent dopant and the secondlayer 344 includes the delayed fluorescent dopant, the first host of thefirst layer 342 may be same as a material of the EBL 330. In thisinstance, the first layer 342 may have an electron blocking functionwith an emission function. Namely, the first layer 342 may serve as abuffer layer for blocking the electron. When the EBL 330 is omitted, thefirst layer 342 serves as an emitting layer and an electron blockinglayer.

FIG. 8 is a schematic cross-sectional view of an organic light emittingdiode of the present disclosure.

As shown in FIG. 8 , an organic light emitting diode D includes thefirst and second electrodes 160 and 164, which face each other, and theorganic emitting layer 162 therebetween. The organic emitting layer 162includes an EML 440, which includes first to third layers 442, 444 and446 and is positioned between the first and second electrodes 160 and164, a HTL 420 between the first electrode 160 and the EML 440 and anETL 460 between the second electrode 164 and the EML 440.

In addition, the organic emitting layer 162 may further include a HIL410 between the first electrode 160 and the HTL 420 and an EIL 470between the second electrode 164 and the ETL 460.

Moreover, the organic emitting layer 162 may further include an EBL 430between the HTL 420 and the EML 440 and a HBL 450 between the EML 440and the ETL 460.

In the EML 440, the first layer 442 is positioned between the secondlayer 444 and the third layer 446. Namely, the second layer 444 ispositioned between the EBL 430 and the first layer 442, and the thirdlayer 446 is positioned between the first layer 442 and the HBL 450.

The first layer 442 (e.g., a first emitting material layer) may includethe organic compound of the present disclosure as a first host and adelayed fluorescent dopant as a first dopant, and the second layer 444(e.g., a second emitting material layer) may include a second host and afluorescent dopant as a second dopant. The third layer 446 (e.g., athird emitting material layer) may include a third host and afluorescent dopant as a third dopant. The fluorescent dopant in thesecond and third layers 444 and 446 may be same or different. The secondand third hosts may be the organic compound of the present disclosure.The delayed fluorescent dopant has a singlet energy being larger thanthe fluorescent dopant.

In the organic light emitting diode D, the singlet energy and thetriplet energy of the delayed fluorescent dopant are transferred intothe fluorescent dopant in the second layer 444 and/or the third layer446 such that the emission is generated from the fluorescent dopant.

In each of the first to third layers 442, 444 and 446, the first tothird hosts may have a percentage by weight being larger than the firstto third dopants, respectively. In addition, the percentage by weight ofthe delayed fluorescent dopant (i.e., the first dopant) in the firstlayer 442 may be greater than that of each of the fluorescent dopant(i.e., the second dopant) in the second layer 444 and the fluorescentdopant (i.e., the third dopant) in the third layer 446.

The singlet energy of the first host is greater than that of the delayedfluorescent dopant, and the triplet energy of the first host is greaterthan that of the delayed fluorescent dopant. In addition, the singletenergy of the second host is greater than that of the fluorescent dopantin the second layer 444, and the singlet energy of the third host isgreater than that of the fluorescent dopant in the third layer 446.

As mentioned above, since the organic compound of the present disclosurehas high triplet energy, the energy transfer efficiency into the delayedfluorescent compound is increased such that the emitting efficiency ofthe organic light emitting diode D is improved.

In addition, since the organic compound of the present disclosure havingthe n-type property is included in the EML as the host, the quenchingproblem of the exciton by an interaction between the triplet exciton ofthe dopant and the hole-polaron is prevented such that the emittingefficiency of the organic light emitting diode D is further improved.

For example, the second host in the second layer 444 may be same as amaterial of the EBL 430. In this instance, the second layer 444 may havean electron blocking function with an emission function. Namely, thesecond layer 444 may serve as a buffer layer for blocking the electron.When the EBL 430 is omitted, the second layer 444 serves as an emittinglayer and an electron blocking layer.

The third host in the third layer 446 may be same as a material of theHBL 450. In this instance, the third layer 446 may have a hole blockingfunction with an emission function. Namely, the third layer 446 mayserve as a buffer layer for blocking the hole. When the HBL 450 isomitted, the third layer 446 serves as an emitting layer and a holeblocking layer.

The second host in the second layer 444 may be same as a material of theEBL 430, and the third host in the third layer 446 may be same as amaterial of the HBL 450. In this instance, the second layer 444 may havean electron blocking function with an emission function, and the thirdlayer 446 may have a hole blocking function with an emission function.Namely, the second layer 444 may serve as a buffer layer for blockingthe electron, and the third layer 446 may serve as a buffer layer forblocking the hole. When the EBL 430 and the HBL 450 are omitted, thesecond layer 444 serves as an emitting layer and an electron blockinglayer and the third layer 446 serves as an emitting layer and a holeblocking layer.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic light emitting diode, comprising: afirst electrode; a second electrode facing the first electrode; and afirst emitting material layer between the first and second electrodesand including a delayed fluorescent compound as a first dopant, and anorganic compound as a first host, the organic compound is of formula:

wherein each of X, Y, and Z is independently selected from hydrogen anda C1 to C20 alkyl group, and at least one of Y and Z is selected fromthe C1 to C20 alkyl group, and wherein each of D1 and D2 isindependently selected from a C10 to C60 heteroaryl group.
 2. Theorganic light emitting diode according to claim 1, wherein at least oneof Y and Z is methyl, and each of D1 and D2 is selected from the groupconsisting of substituted or non-substituted carbazolyl, substituted ornon-substituted dibenzofuranyl and substituted or non-substituteddibenzothiophenyl.
 3. The organic light emitting diode according toclaim 2, wherein each of D1 and D2 is substituted by a carbazole groupor a cyano group.
 4. The organic light emitting diode according to claim1, wherein the organic compound is selected from the group consistingof:


5. The organic light emitting diode according to claim 1, wherein thefirst dopant is:


6. The organic light emitting diode according to claim 1, wherein thefirst emitting material layer further includes a fluorescent compound asa second dopant.
 7. The organic light emitting diode according to claim6, wherein the first host is:


8. The organic light emitting diode according to claim 1, furthercomprising: a second emitting material layer including a second host anda fluorescent compound as a second dopant and positioned between thefirst electrode and the first emitting material layer.
 9. The organiclight emitting diode according to claim 8, further comprising: a thirdemitting material layer including a third host and a fluorescentcompound as a third dopant and positioned between the second electrodeand the first emitting material layer.
 10. An organic light emittingdisplay device, comprising: a substrate; an organic light emitting diodedisposed on or over the substrate, the organic light emitting diodeincluding: a first electrode; a second electrode facing the firstelectrode; and a first emitting material layer between the first andsecond electrodes; and a thin film transistor positioned between thesubstrate and the organic light emitting diode and connected to theorganic light emitting diode, wherein the first emitting material layerincludes a delayed fluorescent compound as a first dopant, and anorganic compound as a first host, the organic compound is of formula:

wherein each of X, Y, and Z is independently selected from hydrogen anda C1 to C20 alkyl group, and at least one of Y and Z is selected fromthe C1 to C20 alkyl group, and wherein each of D1 and D2 isindependently selected from a C10 to C60 heteroaryl group.
 11. Theorganic light emitting display device according to claim 10, wherein atleast one of Y and Z is methyl, and each of D1 and D2 is selected fromthe group consisting of substituted or non-substituted carbazolyl,substituted or non-substituted dibenzofuranyl and substituted ornon-substituted dibenzothiophenyl.
 12. The organic light emittingdisplay device according to claim 11, wherein each of D1 and D2 issubstituted by a carbazole group or a cyano group.
 13. The organic lightemitting display device according to claim 10, wherein the organiccompound is selected from the group consisting of:


14. The organic light emitting display device according to claim 10,wherein the first dopant is:


15. The organic light emitting diode according to claim 2, wherein eachof D1 and D2 is selected from the group consisting of substituted ornon-substituted carbazolyl, and non-substituted dibenzofuranyl, and asubstituent in the substituted carbazolyl, if present, is a carbazolegroup or a cyano group.
 16. The organic light emitting display deviceaccording to claim 11, wherein each of D1 and D2 is selected from thegroup consisting of substituted or non-substituted carbazolyl, andnon-substituted dibenzofuranyl, and a substituent in the substitutedcarbazolyl, if present, is a carbazole group or a cyano group.